Basecamp is a popular and powerful web-based project collaboration and management service from 37signals, makers of other TUAW favorites like Backpack and Highrise. Fortunately, even though Basecamp is web-based, 37signals provides a rich API with which 3rd party developers can make all sorts of neat apps and widgets that tie into the service. A group of students did just that for a class project, resulting in Avalanche, a free Basecamp widget for Yahoo! Widgets.
While I don't use Basecamp to any serious degree, Avalanche seems to be pretty feature-filled, offering access to all your Basecamp messages, todos, time entries, contacts and milestones. Going above and beyond, however, the 37signals blog reports that Avalanche includes features not found in Basecamp, such as auto time entry, spreadsheet generation of time reports, time estimate tracking and contact exporting (which I thought Basecamp already did).
Ultimately, Avalanche looks like an impressive widget for a service loved by its vast and growing base of users. Of course, as with many other widgets, Avalanche is offered free from Avalanche-widget.org.